Exhaust emission control device

ABSTRACT

A device comprising a control valve mounted in an exhaust passage for reducing pulsation of an exhaust emission, when the engine is started, in order to keep the recombustion of exhaust gases in an after-burner or the like from becoming unstable due to the effect of pulsation of the exhaust emission on the recombustion of exhaust gases.

United States Patent 1191 Hosho et a1. 5] Dec. 9, 1975 EXHAUST EMISSION CONTROL DEVICE 3,234,924 2/1966 May 60/292 3,406,515 10/1968 Behrens 60/292 [75] Inventors: Yuk") K 3,577,728 5/1971 Brimer 1 60/303 oyama Hltachl; -l Karl), 3,805,523 4/1974 Tana sawa 60/307 Katsuta, all of Japan I [73] Assignee: Hitachi, Ltd., Japan Primary Examiner-Douglas Hart [22] Flled 1973 Attorney, Agent, or FirmCraig & Antonelli [21] Appl. No.: 406,956

[30] Foreign Application Priority Data Oct. 20, 1972 Japan 47-104474 [57] ABS CT [52] U.S. Cl. 60/284; 60/287; 60/289; A device comprising a control valve mounted in an 60/303; 60/307; 23/277 C haust passage for reducing pulsation of an exhaust [51] Int. C1. F01N 3/10 mission, when the engine Started, in Order to p [58] Field of Search 60/292, 303, 287, 307, the recombustion of exhaust gases in an after-burner 60/284, 289; 23/277 C or the like from becoming unstable due to the effect of pulsation of the exhaust emission on the recombus- [56] References Cited tion of exhaust gases.

UNITED STATES PATENTS 2,981,057 4/1961 Buttler 60/292 1 Claim, 7 Drawing Figures US. Patent Dec. 9 1975 Sheet 1 of 2 3,924,407

US. atent Dec. 9 1975 Sheet 2 of2 3,924,407

THE DEVICE ACCORDING TO THE PRESENT INVENTION THE PRIOR ART DEVICE EXHAUST GASES THE TEMPERATURE WARMING- UP TIME EXHAUST EMISSION CONTROL DEVICE This invention relates to exhaust emission control devices, and more particularly it is concerned with an exhaust emission control device which permits noxious components of an exhaust emission to be removed therefrom by initiating the recombustion of exhaust gases at the early states of engine operation.

A thermal reactor or after-burner is employed in devices for removing noxious components of an exhaust emission vented to atmosphere by mixing secondary air with exhaust gases from the engine and subjecting such mixture to recombustion so as to burn unburnt components contained in large volumes in the exhaust gases from the engine. In order that removal of noxious components of exhaust gases may be carried out by recombustion with a high degree of efficiency, it is necessary that recombustion of the noxious components be effected over a wide range of engine speeds or it is necessary that recombustion be started as early as possible after the engine is started.

However, difficulty is experienced in starting recombustion of exhaust gases as soon as the engine is started. Reasons for this phenomenon are that the noxious exhaust gases delivered to an exhaust emission control device contain a large volume of residual gases, and that the temperature of exhaust gases delivered to the control device is low because the engine, exhaust manifold and exhaust emission control device are low in temperature immediately after the engine is started. To obviate this disadvantage, proposals have been made to raise the temperature of exhaust gases by delaying the ignition of an air-fuel mixture, to supply a recombustion initiating fuel to an after-burner or other means of recombustion, attaching an auxiliary burner to one side of the means of recombustion for producing flames, and using a multiple pipe as means of recombustion to prevent radiation of heat for raising the temperature of a combustion zone as early as possible. All the methods proposed so far have the disadvantage of having to use control means of complex construction. Besides, the method relying on an auxiliary burner has the danger of backfiring. Thus all the methods mentioned above are not fit for practical use.

This invention has as its object the provision of an exhaust emission control device for an internal combustion engine which obviates the disadvantages of the prior art and which permits exhaust gases from the engine to be subjected to recombustion as soon the engine is started whereby noxious components of the exhaust gases can be removed satisfactorily.

The outstanding characteristic of the invention is that an exhaust emission pulsation reducing mechanism comprising throttle means or control means is provided in a passageway for the movement of the exhaust emission from the engine to means of recombustion, so that exhaust gases can be supplied to the means of recombustion through the throttle means or the like when the engine is started or it is being warmed up and the effect of pulsation of exhaust gases on their recombustion can be eliminated. By this arrangement, it is possible to effect control of exhaust emissions with a high degree of precision.

FIG. 1 is a schematic vertical sectional view of the exhaust emission control device of the vortex afterburner type comprising one embodiment of the invention;

FIG. 2 is a fragmentary view showing the control valve of FIG. 1 on an enlarged scale;

FIG. 3 and FIG. 4 are schematic vertical sectional views of exhaust emission control devices comprising other embodiments of the invention;

FIG. 5 is a graph showing changes in the temperature of combustion gases in the means of recombustion;

FIG. 6 is a schematic vertical sectional view of the exhaust emission control device of the afterburner type comprising still another embodiment of the invention; and

FIG. 7 is a sectional view taken along the line VII- VII of FIG. 6.

The invention will be described with reference to an embodiment in which the exhaust emission pulsation reducing mechanism is incorporated in an exhaust emission control device of the vortex after-burner type. In FIG. 1 and FIG. 2, 1 is an exhaust inlet port, 2 an exhaust passage, 3 an after-burner, 4 a gas nozzle for supplying noxious exhaust gases from the engine through the exhaust passage 2 to the after-burner 3 in vortex flow, 5 a secondary air passage for introducing secondary air for recombustion delivered as by an air pump into the after-burner 3 in vortex flow, and 6 an ignition plug mounted in the after-burner 3. 7 is an exhaust emission outlet port for venting the exhaust gases to atmosphere as through a muffler (not shown) after the exhaust gas are rendered clean by recombustion, 8 a control valve mounted in the exhaust passage 2, 9 a throttle opening formed in the control valve 8, and 10 a valve stem integral with the control valve 8. 11 is a bimetal member connected at one end thereof to the valve stem 10 and fixed at the other end to an immovable member (not shown). 12 is a hot gas inlet passage while 13 is a hot gas outlet passage.

In FIGS. 3 and 4, 14 is a lever secured to the valve stem 10 for opening and closing the control valve 8. 15 is a diaphragm means connected by a link to the level 14. 16 is a negative pressure passage for transmitting the pressure in an intake manifold to the diaphragm means 15 therethrough. 17 is a bypass passage for bypassing an exhaust gas stream introduced through the exhaust inlet port 1. 18 is a throttle opening formed in the bypass passage 17. 19 is a rod connecting the lever 14 to a choke mechanism of a carburetor (not shown), and 20 a rod connecting the lever 14 to a carburetor throttling or accelerating mechanism.

In operation, noxious exhaust gases from the engine are introduced into the exhaust emission control device through the exhaust passage 2 and converted into a stream of vortex flow by the gas nozzle 4 tangentially mounted at an entrance to the after-burner 3. The stream of exhaust gases in vortex flow is mixed with secondary air introduced through the secondary air passage 5 into the after-burner 3, and the mixture is ignited by the ignition plug 6. Thus the exhaust gases are subjected to recombustion so as to remove noxious components therefrom and render them clean.

When the engine is started, the stability of engine operation is low and pulsation of an exhaust emission is increased as compared with the engine after being warmed up because the engine and other parts are low in temperature. This phenomenon of pulsation of the exhaust emission greatly influences the recombustion of the exhaust gases. More specifically, as soon as the engine is started, exhaust gases are burned in the afterburner 3 after a mixture of exhaust gases and secondary air is ignited by the ignition plug and flames are produced. The flames produced in the initial stage are unstable because most of their heat is absorbed by the after-burner 3 itself and a heat insulating material therearound. Moreover, the exhaust gases supplied to the after-burner 3 immediately after the engine is started are low in temperature, so that the flames spread rather slowly to the unburnt exhaust gases. Besides, changes in the rate of flow of the exhaust gases result in recombustion of the exhaust gases being unstable, so that the exhaust gases are not thoroughly cleaned. These phenomena are accounted for by the facts that the unburnt components of the noxious exhaust gases supplied to the after-burner 3 pass therethrough without being thoroughly heated, and that the changes in the flow rate of exhaust gases supplied to the after-burner 3 exceed the rate at which the flames spread to unburned exhaust gases in the after-burner.

The exhaust emission pulsation reducing mechanism provided by the invention to reduce the pulsation of an exhaust emission and permit the exhaust gases to be burned again thoroughly comprises the control valve 8 formed with the throttle opening 9 and mounted in the exhaust passage 2. The control valve 8 is closed when the engine is started and while it is being warmed up so as to reduce changes in the rate of flow of the exhaust emission. The mechanism can achieve satisfactory results if it is actuated when pulsation of the exhaust emission becomes larger with engine idling or at low load and low speed.

The exhaust emission pulsation reducing mechanism shown in FIG. 1 operates such that a high temperature gas produced by recombustion in the after-burner 3 is circulated through the hot gas inlet passage 12 and hot gas outlet passage 13 to the bimetal member 10, and the control valve 8 is opened and closed by the bimetal member which responds to the temperature of the hot gas from the afterburner 3. As the control valve 8 is closed, pulsation of the exhaust gases can be reduced by means of the throttle opening 9.

In the embodiment shown in FIG. 3, the control valve 8 is opened and closed by the diaphragm means 15 actuated by changes in the pressure in an intake manifold. The pressure in the intake manifold is transmitted through the negative pressure passage 16 to the diaphragm means 15 so that the control valve can be opened and closed. In this embodiment, the pressure in the intake manifold shows no great fall while the engine operates at cranking speed immediately after being started, so that the rod 19 connected to the choke mechanism is provided to forcedly close the control valve 8.

The embodiment shown in FIG. 4 operates such that the control valve 8 mounted in the exhaust passage 2 is opened and closed in conjunction with the operation of an accelerating or throttling mechanism to which the valve is connected through the rod 20. The throttle opening 18 is formed in the bypass passage 17. This embodiment achieves the same results in operation as the embodiment shown in FIG. 3.

The provision of the exhaust emission pulsation control mechanism including a throttle opening provided in the exhaust passage 2 has the effects of reducing pulsation of an exhaust emission which influences recombustion of exhaust gases in the after-burner and stabilizing the flames produced in the after-burner. FIG. 5 shows changes in the temperature of exhaust gases in the exhaust emission control device of the after-burner type incorporating therein the invention and the temperature of exhaust gases in the same type of the prior art device. It will be seen that the exhaust gases in the after-burner according to the invention are quickly heated, so that the invention can clean the exhaust emission with high efficiency.

It is to be understood that the control valve 8 can be opened and closed by means of a solenoid by sensing the temperature of burning gases in the after-burner or the temperature of walls of the after-burner.

Another embodiment is shown in FIGS. 6 and 7. In this embodiment, the exhaust emission pulsation reducing mechanism is incorporated in an exhaust emission control device of the type in which the after-burner 3 consists of a precombustion chamber 31, a first combustion chamber 32 and a second combustion chamber 33 and an exhaust emission is introduced tangentially into the precombustion chamber 31. Air is introduced also tangentially into the first and second combustion chambers 32 and 33 through secondary air branch passages 51 and 52 and ports 51a and 52a respectively from the secondary air passage 5.

The secondary air passage 5 also has another branch passage 53 vented to atmosphere and provided with a valve 54 which is operatively connected through a connector 55 to the control valve 8 so that the valve 54 may be closed when the control valve 8 is closed.

The exhaust gases supplied into the precombustion chamber 31 are introduced in vortex flow into the first combustion chamber 32 into which air is supplied tangentially through the first port 51a so that laminar combustion takes place. The exhaust gases move in vortex flow into the second combustion chamber 33 into which air is supplied tangentially through the second port 52a. Thus complete combustion of exhaust gases and protection of walls of the combustion chamber are provided for.

The control valve 8 is closed when the engine is at low temperature and being warmed up immediately after it is started, and at the same time the valve 54 in the air branch passage 53 is also closed to supply a relatively large volume of air to the first and second combustion chambers 31 and 32. Generally, a rich air-fuel mixture is supplied to the engine when it is started or being warmed up and exhaust gases naturally contain large proportions of unburnt noxious components. Therefore, it is desirable to supply a large volume of air to the after-burner at this time. With a rise in the temperature in the engine, the proportions of unburnt noxious exhaust components decrease. At this time, the valve 54 is opened to reduce the volume of air supplied to the after-burner. In the embodiment shown and described, the air pump is operated by the vehicle engine and consequently the volume of air supplied to the after-burner per unit hour increases with an increase in the number of revolutions of the engine. Thus the invention is effective to increase the supply of air to the after-burner when the engine temperature is low, so that air can be supplied to the after-burner in a volume necessary for burning exhaust gases per unit volume thereof. The supplied air volume is larger when the engine temperature is lower.

From the foregoing, it will be appreciated that, by actuating the secondary air volume control valve 54 in conjunction with the control valve 8 for reducing the effect of pulsation of exhaust gases on the recombustion of exhaust gases, it is possible to control recombustion in the after-burner with a high degree of precision.

We claim:

1. An exhaust emission control device for rendering noxious exhaust gases from an engine clean by supplying air thereto and subjecting them to recombustion, comprising an exhaust emission pulsation reducing means disposed mediately in a passage of an exhaust emission introduced from the engine to recombustion means for throttling the exhaust gases flowing through said passage when the engine is started and while it is being warmed up, and for enlarging the cross-sectional area of the passage when the engine operates at higher speeds, wherein recombustion is effected in an afterburner comprising a precombustion chamber, a first combustion chamber downstream of said precombustion chamber, and a second combustion chamber to said first and second combustion chambers. 

1. An exhaust emission control device for rendering noxious exhaust gases from an engine clean by supplying air thereto and subjecting them to recombustion, comprising an exhaust emission pulsation reducing means disposed mediately in a passage of an exhaust emission introduced from the engine to recombustion means for throttling the exhaust gases flowing through said passage when the engine is started and while it is being warmed up, and for enlarging the cross-sectional area of the passage when the engine operates at higher speeds, wherein recombustion is effected in an afterburner comprising a precombustion chamber, a first combustion chamber downstream of said precombustion chamber, and a second combustion chamber downstream of said first combustion chamber with passage means connected with said first and second combustion chambers for tangentially introducing secondary air thereinto, said secondary air passage means being provided with valve means for controlling the supply of air to said first and second combustion chambers operatively connected with said throttling means such that when the emission gases to the aFterburner are being throttled when the engine is started and being warmed up the secondary air valve means is closed so as to supply a relatively large volume of secondary air to said first and second combustion chambers. 